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  1. #1
    Join Date
    Jul 2008
    Posts
    7

    Seeking advice on furnace & AC replacement

    I have a 20 year old CM 150,000 btu furnace (all 4 furnace pros I've had out have said it was way oversized) and a 17 year old 3 ton Miller AC in my 45 year old ranch with 1700 sq. ft. living space and 1500 sq. ft. basement in a Detroit suburb. I've been educating myself, talked to 4 HVAC pros and would rather spend more $$ up front to lower annual heating/cooling costs as I expect natural gas to keep rising. The furnace I think I'm going with is the Amana AMV90704CX, which has an AFUE of 95.5% and a 14 or 16 SEER AC, such as the ASX140361A. The company I think I'm going with is small; owner, secretary, 4 techs and they've been in business almost 30 years. He seems honest and knows his stuff and a couple of the techs have been with him 10 and 20 years. I have asked a lot of questions and have heard satisfactory answers for the most part but I have a couple concerns and would like some advice. I've read gradual curves are "required" on the pvc intake and exhaust but this guy said he uses sharp corners but uses 3 inch pvc where 2 inch is called for, as I believe my probably new furnace does. The other concern is he doesn't "strictly" use the Manual-J method of calculating the required sizes. He said he looks at home age, design, insulation, windows and uses experience. None of the 4 pros I've talked use seem to use the full Manual-J method but some modified version. Should these two concerns bother me? What other questions could I ask to insure I'm getting a good installer as I've read brand is not nearly as important as the installation. Thank you so much for such a great resource!
    Jeff

  2. #2
    Join Date
    Apr 2008
    Location
    Alberta Canada
    Posts
    2,246
    Becareful not to oversize venting to much. Could cause air turbulance and flame sensing issues. Manual J is preffered but not everyone does this.
    Do it right the first time.

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Ask those that say brand is NOT a factor,what brand they sell most ofen?Think about it.

  4. #4
    Join Date
    Jul 2008
    Location
    Southeast michigan
    Posts
    93
    theres a good company in melvidale you may want to talk to. i used to work there til i moved to nc. id give them a call. there small and been around for 50 yrs.

  5. #5
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,611
    3 ton for 1700 sq ft in Motown seems high! Find someone who does believe in the Manual J!

    Also, what 'burb? We have some fine Detroiters on here who could service your area and do it right.

  6. #6
    Join Date
    Jul 2008
    Posts
    7
    I'm in Clarkston. 3 of 4 said they'd put in a 3 ton AC while one said he'd put in a 2.5 or 3 ton.

    Knott, can you name the company in Melvindale or is that against the rules?

    Thanks!

  7. #7
    Join Date
    Aug 2008
    Location
    Delaware Ohio
    Posts
    80
    Quote Originally Posted by jgirard View Post
    I'm in Clarkston. 3 of 4 said they'd put in a 3 ton AC while one said he'd put in a 2.5 or 3 ton.

    Knott, can you name the company in Melvindale or is that against the rules?

    Thanks!
    Hey jgirard
    I found a sizing calculator that might help.
    http://www.hvacopcost.com/equipsize.html

    The calculator comes out to 2.8 tons for your house size.. maybe thats why one guy said 2.5 or 3 ton

    I am in the same boat.. kinda.. cuz my house is 1200 square feet..... the calculator says i need 2.2 tons.. i've had quotes for 2 ton and 2.5 ton. I am not sure if its better to go bigger or smaller than you need
    Last edited by panaman; 08-05-2008 at 09:48 AM.

  8. #8
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,791
    Quote Originally Posted by panaman View Post
    Hey jgirard
    I found a sizing calculator that might help.

    The calculator comes out to 2.8 tons for your house size.. maybe thats why one guy said 2.5 or 3 ton

    I am in the same boat.. kinda.. cuz my house is 1200 square feet..... the calculator says i need 2.2 tons.. i've had quotes for 2 ton and 2.5 ton. I am not sure if its better to go bigger or smaller than you need
    That thing is just a guess.

    For my place(1650 sq ft) it says 3 tons.
    I have 2.5 tons, and thats over sized for my place by 9,000 BTUs.

    There is no quick 1 minute calculation that will tell you what size you need.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  9. #9
    Join Date
    Aug 2008
    Location
    Delaware Ohio
    Posts
    80
    Quote Originally Posted by beenthere View Post
    That thing is just a guess.

    For my place(1650 sq ft) it says 3 tons.
    I have 2.5 tons, and thats over sized for my place by 9,000 BTUs.

    There is no quick 1 minute calculation that will tell you what size you need.
    yeah, I am sure your right. Floor plan prolly has something to do with it.
    I would think a ranch style house would need a smaller unit compared to a 2 story? Is this a correct thinking measure?

  10. #10
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,791
    Your on the right track.

    A 2000 sq ft rancher, has more heat gain through the ceiling then a 2000 sq ft 2 story with the same attic insulation.

    A 2000 sq ft 1½ story can have more heat gain then a 2 story 200 sq ft.(knee walls)

    Orientation of the house makes a big difference also.

    Window type.
    Sky lights.
    Can lights.
    Number of people.
    Attached garage or not.
    ETC.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  11. #11
    Join Date
    Jul 2008
    Posts
    7
    Thanks for the feedback everyone. Of the 4 pros I've had out here, 1 never got back to me - hard to imagine why in what is supposed to be a bad economy. The other 3 all seem competent and I'm kind of down to two based on recommended models. Of those two the prices are significantly different. They seem equally competent so I'm wondering does the lower guy not know what he's doing or is the higher guy gouging? At this point I'm inclined to believe it's the latter. Any suggestions on questions to ask to insure they really know their stuff?

  12. #12
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,791
    Look at the proposals/estimates.
    Are they both doning the same things.

    Maybe the higher priced guy is doing more. Maybe not.

    Higher guy might be using sheet metal, and the lower guy might be using duct board transitions.
    Are any of them testing performance.
    The higher guy, may send his men to more training then the other. ( You do want trained techs working on your equipment don't you )
    If they gave you model numbers. Post them here.
    One might be using a higher line of equipment then the other.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  13. #13
    Join Date
    Jul 2008
    Posts
    7
    Both quotes are for the same equipment. The furnace is the Amana AMV90704CX and the AC is the ASX140361A. What are duct board transitions? Is this a cheap substitute for sheet metal?

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